Are you merging directly to the printer, or to a new document, then printing from there? If it's the former, try merging to a new document and checking whether the page layout is correct.

Also, have you checked that you're using the correct drivers, etc? These are fairly ancient printers, and drivers for them aren't included with Windows 7. You may need to use a Windows 7 driver for a similar printer (eg an Epson LQ driver).